pc transformer

If you know the internal resistances of the transformer, the cores losses and the turns ratios of the windings, you might be a able to infer something about the currents flowing in the transfomer from the difference between the non-load output voltage, given by the input voltage and the turns ratio, and the actuall output voltage under load.

Because transformers are complicated objects, you won't be able to infer anything particularly precise unless you know a great deal about the cores losses (and the way they change with temperature and frequency) and skin effect, which makes winding resistance a function of the frequency of the current flowing through the windings.

The harmonic content of the current flowing the secondary of the transformer in a pc switching power supply is yet another complicated question.

A Hall effect current sensor to measure the current in the wires in the mains lead might get you the desired information rather more easily.

-- Bill Sloman, Nijmegen

The short answer is "no."

John

PCs use switchers. I've seen switchers that had negative output impedances.

John